It has long been known and has been common, for the production of yarns, to utilize spinning processes in which the spindles are provided below the usually fixed thread guide with respective spinning heads. These spinning heads rotate with the spindles or in certain variants approximately with the speed of the spindles and bring the twist in the yarn relatively close to the nip of the supply rollers.
The thread balloon is thereby suppressed and the yarn can be wound up with reduced tension on the bobbin. Advantages are also obtained from the viewpoint of the travel characteristics of the traveller.
Such a process has not become widely used in practice. The reasons for this differ substantially.
The use of spinning heads results in a movement of the twist of the yarn from close to the nip of the rollers from which the slubbing is supplied to the spinning zone. The spun yarn which results is then guided via the entrainer of the spinning head in a spiral pattern from a part of the bobbin sleeve to the traveler of the spinning ring. It has been found that this spinning process gives rise to a very hairy yarn.
The use of the process is limited, therefore, to the spinning of such yarns in which the hairiness is desirable. These are yarns for carpentry, for covers or for felts (see the brochure of the Rieter firm for Carded Yarn Ring Spinning Machine H3 from the year 1967).
For the production of very fine and smooth yarn, especially combed yarn, for fabrics the hairiness of the yarn is undesirable. The spinning process with a suppressed yarn balloon is therefore not used for this purpose.
With the aim of increasing the quality of yarn spun by means of a spinning head, attempts have been made to displace the thread guide above the spinning head in a transition from balloon reduced spinning to spinning with a yarn balloon (DE 34 15 977 A1 and 34 15 998 A1). This approach has also not been crowned with success. The hairiness of the yarn by spinning with a spinning head and suppressed yarn balloon is not avoided by the displacement of the yarn guide.
For the aforementioned reasons it is preferred for the spinning of finer yarns, especially finer carded (worsted) or combed yarn, to carry out the spinning with a reduced yarn balloon with the aid of so-called balloon-limiting rings. However, increases in spinning speed and increases in the output of the spinning machine are thereby limited.
In the use of this process there has been increasing employment of so-called compaction zones in the region of the output rolls of the drafting frame (DE 882 066) or following the drafting frame (EP 0 635 590 A2 or 197 08 410 A1). These compaction zones seek to draw the fibers of the drafted slubbing into a reduced width in the nip of the supply rollers (rollers which feed the slubbing into the spinning zone). The result is a very small spinning triangle. The danger of yarn breakage is thus significantly reduced at these locations.